1. Technical Field
A rotary fluid machine and a method of operating the machine are disclosed. The rotary fluid machine that may be operated as either a pump or a motor.
2. Background Art
One type of rotary fluid machine comprises a rotor and a stator, one fitted inside the other so as together define a working fluid space. A plurality of lobes is formed on one of the rotor or the stator, and a plurality of gates is supported by the other. Inlet and outlet ports are provided on opposite sides of each lobe to allow fluid to flow into and out of the working fluid space. The machine can function as a pump or a motor. In particular by driving the rotor with say an electric motor the machine can act as a pump. Alternately by supplying a high pressure fluid to the inlet ports the machine can operate as a motor.
While there is rotation between the rotor and the stator the gates are moved between respective extended (or sealing) and retracted positions dependent on the relative juxtaposition of the rotor and the stator. When a gate is passing a lobe crest, the gate will be in its retracted position. Conversely when a gate is disposed between adjacent lobe crests it will be in its partly or fully extended position. In order to maintain optimum operational efficiency it is preferable that the gates are in close proximity to or in contact with the non-supporting body for at least the portion of their travel between mutually adjacent inlet and outlet ports particularly while the gates are in a fully extended position. To this end the rotary fluid machine is provided with a gate control system that operates to control the motion of a gate and in particular to at least move, urge or otherwise bias the gates to their fully extended positions. The gate control system may comprise for example a plurality of cams one on each side of each gate, and corresponding cam tracks in which the cams run. By appropriate profiling the cam tracks the gates are moved or pulled to their fully extended (sealing) position when there is relative motion between the rotor and stator. The gate control system may also operate to move, urge or otherwise bias the gates to the retracted position. However this function can additionally or alternately be provided by the non-supporting body itself which mechanically push the gates to their retracted positions.
For example assume the machine is configured or operated as a pump and the gates are supported by the rotor. The gate control system operates to maintain the gates in close proximity to, or in contact with a surface of the stator. This is desirable on the suction side in order to draw fluid from a supply through the inlet port. Gate position control is also important on a discharge side to maximise discharge pressure and flow rate.